Fundamentals of Data NetworksCPCS371 بسم الله الرحمن الرحيم Faculty of Computing and Information Technology, KAU Computer Science Department Chapter 1: Introduction

1.1 Data CommunicationsData Communications 1.2NetworksNetworks 1.3The InternetThe Internet 1.4Protocols and StandardsProtocols and Standards

Textbook : Data Communications and Networking, 4 th Behrouz A. Forouzan.

Grading system Participation: 5 First test:10 Second test: 20 Final test: 30 Lab : 20 Quizzes : 15

Introduction Data communications and networking  Change the way we do business and the way we live  Business decisions have to be made more quickly  Decision depends on immediate access to accurate information  Business today rely on computer networks and internetworks  Before get hooked up, we need to know: How networks operate What types of technologies are available Which design best fills which set of needs

Introduction  Development of the PC changes a lot in business, industry, science and education.  Similar revolution is occurring in data communication and networking Technologies advances are making it possible for communications links to carry more and faster signals Services are evolving to allow the use of this expanded capacity For example telephone services extended to have: Conference calling Call waiting Voice mail Caller ID

1.1 Data Communications Communication: Means sharing information Local (face to face) or remote (over distance) Telecommunication Telephone, telegraph and television Means communication at a distance Tele is Greek for far

Data Communications Data: Refers to information Presented in any form Agreed upon by the parties ( creating & using) Data communication : is the exchange of data between two devices via some form of transmission medium (wire cable).

Data Communications  Communication system made up of a combination of hardware and software  Effectiveness of data communication system depends on: 1.Delivery : The system must deliver data to correct destination. Data received by the indented user only 2.Accuracy: The system must deliver data accurately (no change). Data changed & uncorrected is unusable

Data Communications 3.Timeliness: The system must deliver data in timely manner Data arrived late are useless In the same order (video and audio) & without delay (Real time transmission) 4.Jitter: Variation in the packet arrival time (uneven quality in the video is the result)

Data Communications

Components  A data communication system is made up of five components

Components 1.Message: the information (data) to be communicated –Consist of text, numbers, pictures, audio, or video 2.Sender: the device that sends the data message –Computer, workstation, telephone handset, video camera, … 3.Receiver: the device that receives the message –Computer, workstation, telephone handset, television, ….

Components 4.Medium: The physical path by which a message travels from sender to receiver –twisted pair, coaxial cable, fiber-optic, radio waves

Components 5.Protocol: a set of rules that govern data communications – An agreement between the communicating devices – Devices may be connected but not communicating (no protocol) –Arabic speaker with Japanese speaker

Data Representation Text Audio Video Numbers Images

Text:  Sequence of bits (0s or 1s)  Different sets of patterns to represent text symbols (each set is called: code)  ASCII: 7 bits (128 symbols)  common coding system today is:  Unicode uses: 32 bits to represent a symbol or character in any language Unicode (4,294,967,296)

Data Representation Numbers:  Represented by bit patterns  The number is directly converted to a binary number

Data Representation Images:  Represented by bit patterns  A matrix of  Resolution: size of the pixels  High resolution: more memory is needed  Each pixel is assigned a bit pattern 1-bit pattern (black and white dots image) 2-bit pattern (4 levels of gray) RGB (color images) pixels

Data Representation Audio:  Continuous not discrete  Change to digital signal Video:  Recording or broadcasting of a picture or movie  Change to digital signal

Data Flow Communication between two devices can be:  Simplex  Half-Duplex  Full-Duplex

Data Flow Simplex (one way street)  The communication is unidirectional  Only one device on a link can transmit; the other can only receive  Use the entire capacity of the channel to send data  Example: Keyboards, Monitors Data

Data Flow Half-Duplex (one-lane with two-directional traffic)  Each station can both transmit and receive, but not at the same time  When one device is sending, the other can only receive, and vice versa  The entire capacity of a channel is taken over by the transmitting device  Example: Walkie-talkies Data

Data Flow Full-Duplex (Duplex) (two-way street)  Both stations can transmit and receive at same time  Signals going in either direction sharing the capacity of the link  Sharing can occur in two ways: Link has two physically separate transmission paths One for sending and the other for receiving The capacity of the channel is divided between signals travelling in both directions  Example: Telephone network Data

Exercise What mode of data flow the following exhibits shows? Answer: Full-Duplex Data

Networks  Network : A set of devices (nodes) connected by communication links Node : computer, printer, … -Distributed Processing : -Most networks used it -Task is divided among multiple computers instead of one single large computer

Networks Network Criteria –Network must meet a certain number of criteria –The most important of the network criterions are: –Performance –Reliability –Security

Networks Performance  T ransit time: A mount of time required for a message to travel from one device to another  Response time: Elapsed time between an inquiry and a response

Networks Performance  Performance depends on : 1- Number of users: large number slow response time. 2- Type of transmission medium: fiber-optic cabling faster than others cables. 3- Capabilities of the connected hardware: affect both the speed and capacity of transmission. 4- Efficiency of the software: process data at the sender and receiver and intermediate affects network performance.

Networks Performance  Performance is evaluated by two contradictory networking metrics: Throughput (high): a measure of how fast we can actually send data through a network Delay (low)

Networks Reliability  Reliability is measured by: 1.Frequency of failure 2.Recovery time of a network after a failure 3.Network’s robustness in a catastrophe: protect by good back up network system

Networks Security  Protecting data from unauthorized access  Protecting data from damage and development  Implementing policies and procedures for recovery from breaches and data losses (Recovery plan)

Networks Physical Structures:  Type of connection Network: Two or more devices connected through links Link: Communication pathway that transfers data from one device two another Two devices must be connected in some way to the same link at the same time. Two possible types: Point-to-Point Multipoint

Networks Point-to-Point  Dedicated link between two devices  Entire capacity of the link is reserved for transmission between those two devices  Use an actual length of wire or cable

Networks Point-to-Point  Other options, such as microwave or satellite is possible  Example: Television remote control

Networks Multipoint (multidrop)  More than two devices share a single link  Capacity is shared  Channel is shared either spatially or temporally Spatially shared: if devices use link at same time Timeshare: if users must take turns

Networks Physical Topology  The way a network is laid out physically  Two or more links form a topology  The topology of a network is the geometric representation of the relationship of all the links and linking devices (nodes) to one another.  Four topologies : Mesh, Star, Bus, and Ring

Physical Topology

Mesh  Every link is dedicated point-to-point link  The term dedicated means that the link carries traffic only between the two devices it connects

Physical Topology Mesh n n ( n - 1) / 2  To link n devices fully connected mesh has: n ( n - 1) / 2 physical channels (Full-Duplex) n - 1  Every Device on the network must have n - 1 ports

Physical Topology Mesh  Example: 8 devices in mesh has links: n(n-1) / 2 number of links = 8 (8-1)/2 = 28 number of ports per device = n – 1 = 8 –1 = 7

Physical Topology Mesh  Advantages Each connection carry its own data load (no traffic problems) A mesh topology is robust Privacy or security Fault identification and fault isolation

Physical Topology Mesh:  Disadvantages Big amount of cabling Big number of I/O ports Installation and reconnection are difficult Sheer bulk of the wiring can be greater than the available space Hardware connect to each I/O could be expensive Mesh topology is implemented in a limited fashion; e.g., as backbone of hybrid network

Physical Topology Star:  Dedicated point-to-point to a central controller (Hub)  No direct traffic between devices  The control acts as an exchange

Physical Topology Star  Advantages Less expensive than mesh (1 Link + 1 port per device) Easy to install and reconfigure Less cabling Additions, moves, and deletions required one connection Robustness : one fail does not affect others Easy fault identification and fault isolation

Physical Topology Star  Disadvantages Dependency of the whole topology on one single point (hub) More cabling than other topologies ( ring or bus) Used in LAN

Physical Topology Bus  It is multipoint  One long cable acts as a backbone  Used in the design of early LANS, and Ethernet LANs

Physical Topology Bus  Nodes connect to cable by drop lines and taps  Signal travels along the backbone and some of its energy is transformed to heat  Limit of number of taps and the distance between taps

Physical Topology Bus  Advantages Ease of installation Less cables than mesh, star topologies  Disadvantages Difficult reconnection and fault isolation ( limit of taps) Adding new device requires modification of backbone Fault or break stops all transmission The damaged area reflects signals back in the direction of the origin, creating noise in both directions

Physical Topology Ring  Each device has dedicated point-to-point connection with only the two devices on either side of it  A signal is passed along the ring in one direction from device to device until it reaches its destination  Each devices incorporates a Repeater

Physical Topology Ring  Advantages Easy of install and reconfigure Connect to immediate neighbors Move two connections for any moving (Add/Delete) Easy of fault isolation  Disadvantage Unidirectional One broken device can disable the entire network. This weakness can be solved by using a dual ring or a switch capable of closing off the break

Physical Topology Hybrid Topology  Example: having a main star topology with each branch connecting several stations in a bus topology

Categories of Networks Network Category depends on its size Two primary categories  LAN  LAN: Covers area < 2miles  WAN  WAN: Can be worldwide  MAN  MAN: Between LAN & WAN, span 10s of miles

Local Area Network (LAN) Privately owned Links devices in the same office, building, or campus Simple LAN: 2 PCs & 1 printer in home or office Size is limited to a few kilometers Allow resources to be shared (hardware, software, or data)

Local Area Network (LAN) An isolated LAN connecting 12 computers to a hub in a closet

Local Area Network (LAN) LAN is distinguished by:  Size (# users of OS, or licensing restrictions)  Transmission medium (only one type)  Topology (bus, ring, star) Data Rates (speed):  Early: 4 to 16 Mbps  Today: 100 to 1000 Mbps

Wide Area Networks (WAN) Provides long-distance transmission of data over large geographic areas (country, continent, world)

Wide Area Networks (WAN) Switched WAN  Backbone of the Internet Dialup line point-to-point WAN  Leased line from a telephone company

Wide Area Networks (WAN)

Metropolitan Area Networks (MAN) Size between LAN and WAN Inside a town or a city Example: the part of the telephone company network that can provide a high-speed DSL to the customer

Interconnection of Networks: Internetworks Two or more networks connected together

The Internet Internet has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time. Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use An internet is 2 or more networks that can communicate with each other The Internet is a collaboration of more than hundreds of thousands of interconnected networks

The Internet An internet (small i) is two or more networks Notable internet is called the Internet (hundreds of thousands interconnected networks)  Private individuals + government agencies + school + research facilities + Corporations + libraries in more than 100 countries This communication system came in 1969 Mid-1960 (ARPA) Advanced Research Projects Agency in (DOD) was interested to connect mainframes in research organizations 1967, ARPA presented its ideas for ARPANET  Host computer connecting to (IMP) interface message processor.  Each IMP communicate with other IMP 1969, four nodes (universities) connected via IMPs to form a network  Software (NCP) Network Control Protocol provided communication between the hosts. 1972, Vint Cerf and Bob Kahn invented (TCP) Transmission Control Protocol Later TCP was split to (TCP) Transmission Control Protocol and (IP) Internetworking Protocol

The Internet Internet Today  Made of many LANs and WANs  Every day new networks area added and removed  Internet services Providers (ISPs) offer services to the end users International service providers National service providers Regional service providers Local service providers Data rate

The Internet Hierarchical organization of the Internet

Protocols and Standards Protocol synonymous with rule Standards: agreed-upon rules Protocols  A protocol is a set of rules that govern data communications  Defines What, How, and When it is communicated

Protocols and Standards Elements of a protocol:  Syntax: structure or format of data Example: 8-bits address of sender, 8-bits address of receiver  Semantics: meaning of each section of bits Example: Does the address is a route to be taken or the final destination of the message  Timing: when data should be sent and how fast they can be sent Example: sender produces data at 100 Mbps but the receiver can process data at only 1 Mbps  overload and data loose

Standards Essential in creating and maintaining an open and competitive market for equipment manufactures Guaranteeing national and international interoperability of data and telecommunication technology and processes Providing guidelines to manufacturers, vendors, government agencies, and other service providers to ensure the kind of interconnectivity necessary in today’s marketplace and in international communications

Standards Two categories  De facto: not approved by an organized body but adopted as standards through widespread use  De jure: Legislated by an officially recognized body

Standards Standards are developed through the cooperation of:  Standards Creation Committees ISO, ITU-T, CCITT, ANSI, IEEE, EIA  Forums Created by special-interest groups Present their conclusions to the standards bodies  Regulatory Agencies Ministry of Telecommunication and Information Technology (KSA) Purpose: Protecting the public by regulating radio, television, and communication

Standards Internet standards  Tested thoroughly tested specification that is useful to be adhered to by those who work with the Internet  Formalized regulation that must be followed  Specification become Internet standard Begins as Internet draft for 6 months Upon recommendation from the Internet authorities draft published as Request for Comment (RFC) RFC is edited, assigned a number, and made available to all interested parties